A light-emitting diode (which hereafter may also be referred to as “LED”) is generally formed by arranging an LED device on the bottom portion of a cup-shaped sealing member in a package, and sealing it with a sealing resin. Conventionally, as an LED sealing resin, a light-transmitting resin including an epoxy resin, a silicone resin, or the like is used.
However, since a bisphenol A glycidyl ether which is a main component of a common epoxy resin has an absorption at wavelengths shorter than about 400 nm, there was a problem in that coloration caused by oxygen oxidation of an aromatic ring under UV excitation occurs. For this reason, a sealing resin composed of an epoxy resin and an LED in which an LED device is sealed with the sealing resin was required to have improved light resistance together with high reliability.
Furthermore, when using a silicone resin such as a polydimethyl silicone, polydiphenyl silicone or polymethylphenyl silicone, a distortion is generated by the difference in thermal expansion between the silicone resin and a metal wire or an electrode of a lead frame which is to be sealed, resulting in the metal wire being broken or the detachment of the sealing resin from the electrode. Furthermore, when using a sealing resin composed of a silicone resin, because the silicone resin is soft and the strength thereof is low, there was a problem in that the surface of the sealing resin easily becomes dusty, and the silicone resin was easily damaged when the LED is mounted. Therefore, the LED in which an LED device is sealed with the sealing resin composed of the silicone resin was not sufficiently reliable.
Furthermore, as a sealing resin used for an LED, a resin including as a main component a siloxane derivative having an epoxy group and oxetanyl group, or having an epoxy group or an oxetanyl group has been proposed (For example, refer to Patent Document 1). By using the sealing resin described in Patent Document 1, the problem caused by using a transparent resin composed of the epoxy resin or silicone resin can be improved.
However, because the sealing resin described in Patent Document 1 has a high viscosity, there were disadvantages in that the droplet of the sealing resin was difficult to discharge by a dispenser and the cracks were not sufficiently prevented while the sealing resin was cured by heating. Accordingly, the productivity and reliability of the LED in which an LED device was sealed with the sealing resin described in Patent Document 1 was insufficient.
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2004-238589